Epitaxial Dy 2 O 3 Thin Films Grown on Ge(100) Substrates by Molecular Beam Epitaxy
- PDF / 1,462,185 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 45 Downloads / 255 Views
1252-I03-01
Epitaxial Dy2O3 Thin Films Grown on Ge(100) Substrates by Molecular Beam Epitaxy Md. Nurul Kabir Bhuiyan*1, Mariela Menghini1, Christel Dieker2, Jin Won Seo3, Jean-Pierre Locquet1, Roumen Vitchev4 and Chiara Marchiori5 1 Department of Physics and Astronomy, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001, Leuven, Belgium 2 Mikrostrukturanalytik, Christian-Albrechts Universität zu Kiel, Kaiserstrasse 2, D-24143 Kiel, Germany 3 Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001, Leuven, Belgium 4 VITO Materials, Flemish Institute for Technological Research, Boeretang 200, B-2400 Mol, Belgium 5 IBM Research GmbH, Zurich Research Laboratory, Saeumerstrasse 4, 8803, Rueschlikon, Switzerland ABSTRACT Dysprosium oxide (Dy2O3) films are grown epitaxially on high mobility Ge(100) substrates by molecular beam epitaxy system. Reflection high energy electron diffraction patterns and Xray diffraction spectra show that single crystalline cubic Dy2O3 films are formed on Ge(100) substrates. The epitaxial-relationship is identified as Dy2O3 (110)║Ge(100) and Dy2O3 [001]║Ge[011]. Atomic force microscopy results show that the surface of the Dy2O3 film is uniform, flat and smooth with root mean square surface roughness of about 4.6Å. X-ray photoelectron spectroscopy including depth profiles confirms the composition of the films being close to Dy2O3. TEM measurements reveal a sharp, crystalline interface between the oxide and Ge. INTRODUCTION For the fabrication of a high speed transistor a high mobility (high-μ) Ge(100) substrate is important due to both higher electron and hole mobilities than those of Si [1 - 3]. As GeO2 films are thermodynamically unstable at high temperatures, the integration of epitaxial crystalline high dielectric constant (high-κ) thin films on Ge substrates could be possible without the presence of any interfacial GeO2 layers [4, 5]. High-κ dysprosium oxide (Dy2O3) is a promising insulator among the lanthanide metal oxides due to its low hygroscopic nature [6]. The challenge is to grow epitaxial Dy2O3 thin films on high-μ Ge(100) substrates because the lattice mismatch between the bulk Dy2O3 (10.66 Å) and the Ge substrates (5.646 Å) is about 5.6% when the double Ge unit-cell is taken into account [7]. The lattice mismatch of all rare-earth oxides (RE2O3) with the double Ge unit-cell is shown in Fig. 1. The linear thermal expansion coefficient mismatch between Dy2O3 (5.9×10-6/K) and Ge (7.74×10-6/K) is about - 31%. *
Corresponding author: Md. Nurul Kabir Bhuiyan; Tel.: +32 16 32 7228; Fax: +32 16 32 7983;
E-mail address: [email protected]
In this paper, epitaxial Dy2O3 thin films are directly grown on high-μ Ge(100) substrates by molecular beam epitaxy for the first time. Structural, chemical, surface morphological and interfacial properties of the Dy2O3 thin film are investigated in detail by in situ Reflection high energy electron diffraction (RHEED) and ex situ X-ray diffraction (XRD), X-ray photoelectro
Data Loading...
